Added API methods needed for the Intelligent Helpdesk taxonomy: get_childconcepts, snapshot, add_literal, add_custom_attribute, add_custom_relation.
Added API methods needed for the Intelligent Helpdesk taxonomy:
get_childconcepts, snapshot, add_literal, add_custom_attribute,
add_custom_relation.

Also extended add_new_concept to support the `suffix` argument.
get_childconcepts was based on get_corpus_documents, the most
similar api method I could find in the implementation.

artreven/pp_api